8 Partitioning JSON Data

You can partition a table using a JSON virtual column as the partitioning key. The virtual column is extracted from a JSON column using SQL/JSON function json_value.

Partition on a Non-JSON Column When Possible

You can partition a table using a JSON virtual column, but it is generally preferable to use a non-JSON column. A partitioning key specifies which partition a new row is inserted into. A partitioning key defined as a JSON virtual column uses SQL/JSON function json_value, and the partition-defining json_value expression is evaluated each time a row is inserted. This can be costly, especially for insertion of large JSON documents.

Rules for Partitioning a Table Using a JSON Virtual Column

• The virtual column that serves as the partitioning key must be defined using SQL/JSON function json_value.

• The data type of the virtual column is defined by the RETURNING clause used for the json_value expression.

• The json_value path used to extract the data for the virtual column must not contain any predicates. (The path must be streamable.)

• The JSON column referenced by the expression that defines the virtual column can have an is json check constraint, but it need not have such a constraint.

See Also:

Oracle Database SQL Language Reference for information about CREATE TABLE

Example 8-1 Creating a Partitioned Table Using a JSON Virtual Column

This example creates table j_purchaseorder_partitioned, which is partitioned using virtual column po_num_vc. That virtual column references JSON column po_document (which uses CLOB storage). The json_value expression that defines the virtual column extracts JSON field PONumber from po_document as a number.

CREATE TABLE j_purchaseorder_partitioned
  (id VARCHAR2 (32) NOT NULL PRIMARY KEY,
   date_loaded TIMESTAMP (6) WITH TIME ZONE,
   po_document JSON,
   po_num_vc NUMBER GENERATED ALWAYS AS
     (json_value (po_document, '$.PONumber' RETURNING NUMBER)))
  PARTITION BY RANGE (po_num_vc)
   (PARTITION p1 VALUES LESS THAN (1000),
    PARTITION p2 VALUES LESS THAN (2000));